1. Field
The present invention is related to medical systems, devices and methods. More specifically, the invention is related to systems, devices and methods for treating obstructive sleep apnea or snoring.
2. Description of the Related Art
Obstructive sleep apnea (OSA) is a common medical disorder that can be quite serious. Approximately 1 in 22 Americans (about 12,000,000 people) suffer from OSA, and many cases go undiagnosed. Chronic fatigue has long been recognized as the hallmark of OSA, but more recently, large clinical studies have shown a strong link between OSA, strokes and death.
Obstructive sleep apnea is a condition in which the flow of air pauses or decreases during breathing while one is asleep, because the airway has become narrowed, blocked, or floppy. (See FIG. 1A illustrating an airway A during normal breathing and FIG. 1B illustrating the airway A during OSA.) A pause in breathing is called an apnea episode, while a decrease in airflow during breathing is called a hypopnea episode. Almost everyone has brief apnea or hypopnea episodes while they sleep. In OSA, however, apnea episodes occur more frequently and/or last longer than in the general population. OSA has become an increasingly costly medical condition in recent years, as the disorder is more prevalent in obese people and obesity has become significantly more prevalent. Unfortunately, the currently available options for treating OSA are not ideal.
A person with OSA usually begins snoring heavily soon after falling asleep. Often the snoring gets louder. The snoring is then interrupted by a long silent period during which there is no breathing. This is followed by a loud snort and gasp, as the person attempts to breathe. This pattern repeats. Many people wake up unrefreshed in the morning and feel sleepy or drowsy throughout the day. This is called excessive daytime sleepiness (EDS). People with sleep apnea may act grumpy, impatient, or irritable, be forgetful, fall asleep while working, reading, or watching TV, feel sleepy or even fall asleep while driving, or have hard-to-treat headaches. OSA sufferers may also experience depression that becomes worse, hyperactive behavior (especially in children), or leg swelling (if severe).
The most widely used therapy for OSA is Continuous Positive Airway Pressure (CPAP). As shown in FIG. 2, a CPAP system typically 10 consists of a mask 12a-12c fitting in or over the nose or nose and mouth, an air pressurizing console 14 and a tube 16 connecting the two. CPAP works by pressurizing the upper airway throughout the breathing cycle, essentially inflating the airway to keep it open and thus creating what is sometimes referred to as a “pneumatic splint.” Because the masks 12a-12c typically leak air, CPAP systems have to provide an airflow rate of up to 200 liters per minute (approximate figure based on unpublished data). This high flow rate makes breathing feel quite uncomfortable for many patients and requires a relatively large, noisy pressurizing console 14. Additionally, the high required flow rates of CPAP often cause discomfort during exhalation due to increased resistance, as well as nasal dryness, dry mouth, ear pain, rhinitis, abdominal bloating and/or headaches.
The overwhelming shortcoming of CPAP is poor patient compliance. Over half of all patients who try CPAP stop using it. Patients dislike the side effects mentioned above, as well as having to wear an uncomfortable, claustrophobic mask, being tethered to a pressurizing console, the noise of the console, traveling with a bulky device, and a loss of personal space in bed.
Many CPAP devices and alternatives to CPAP have been developed, but all have significant shortcomings. Less invasive attempts at OSA treatment, such as behavior modification, sleep positioning and removable splints to be worn in the mouth, rarely work. A number of different surgical approaches for treating OSA have also been tried, some of which are still in use. For example, Uvulopalatopharyngoplasty (UPPP) and Laser Assisted Uvula Palatoplasty (LAUP) are currently used. Surgical approaches, however, are often quite invasive and not always effective at treating OSA.
One alternative approach to OSA treatment is to provide a pneumatic splint during the expiratory portion of the respiratory cycle by producing a partial blockage in the nose or mouth, thus slowing the release of air during expiration and increasing positive pressure in the airway. The simplest way to form an expiratory pneumatic splint, pursing the lips, has been shown to open the upper airway and improve breathing in emphysema patients. This type of maneuver is generically labeled Expiratory Positive Airway Pressure (EPAP).
Ventus Medical, Inc. (http://www.proventtherapy.com/ventus medical) has developed a removable nasal EPAP device to produce such a pneumatic splint during exhalation (the Provent® Sleep Apnea Therapy). (See, for example, Doshi et al., U.S. Patent Application Pub. No. 2006/0150978.) This device restricts exhalation by forcing expired air through several small orifices attached to the nose. This is labeled a Fixed Orifice Resistor (FOR). One shortcoming of this therapy is that 1) the fixed hole exhalation valve does not have a capped maximum pressure, 2) the pressure increases immediately upon exhalation and therefore makes it difficult to exhale, and 3) with no assistance of additional pressure from an external source, if the patient has an apneic event there is no ‘rescue pressure’. A further disadvantage is that the Provent® device or any FOR restricts expiratory airflow using a fixed hole for resistance. This leads to an uncomfortable spike in nasal pressure at the beginning of expiration when airflow is highest and a less efficacious decrease in nasal pressure at the end of expiration when airflow is lowest. Another shortcoming of the Provent® device is that it produces the pneumatic splint only during exhalation—i.e., there is no increased pressure during inhalation.
In addition, the device is not effective in mouth breathers or patients who become mouth breathers when resistance is added to the nasal passages. Thus, the Provent® device is useful only in moderate cases of OSA that do not convert to mouth breathing.
Although snoring is not as severe a condition as OSA, it does affect lives adversely. Snoring can adversely affect sleep quality and can make sleeping with a spouse or other partner difficult. Although many snoring therapies have been tried, including Breathe Right® Nasal Strips and more invasive approaches in more severe cases, no ideal solution has been found.
Therefore, it would be advantageous to have improved systems, devices and methods for treating OSA and/or snoring. Ideally, such systems, devices and methods would be less cumbersome than currently available CPAP systems, to improve patient compliance. Also ideally, such systems, devices and methods would provide some of the advantages of an expiratory pneumatic splint. At least some of these objectives will be met by the embodiments described in this application.